Conventional motor vehicle suspension systems often include one or more stabilizer bars to control the degree of roll of the motor vehicle during cornering or other vehicle maneuvers. A typical stabilizer bar is generally U-shaped having a long intermediate portion disposed laterally with respect to the motor vehicle and a pair of relatively short end portions extending forwardly or rearwardly to connect to a corresponding pair of suspension arms or wheel hubs. The intermediate portion normally is connected to the underside of the vehicle by one or more bracket assemblies.
The mounting bracket assembly for the intermediate portion of the stabilizer bar typically includes an elastomeric bushing, sometimes termed an insulator, and a bracket which is secured to the underside of the vehicle. The elastomeric bushing is located between the stabilizer bar and the bracket to support and isolate the stabilizer bar. In some applications it is desirable to use an elastomeric bushing that permits the stabilizer bar to rotate freely about the axis of the intermediate portion of the stabilizer bar. In other applications, it is desirable to allow partial wind-up of the bushing and then allowing the bushing to slip for relative torsional travel between the bushing and the bar. In still other applications, attempts are made to eliminate the slippage of the bushing such that all rotation of the stabilizer bar is resisted by wind-up of the bushing.
The designs that allow rotation between the bar and the bushing have attempted to minimize friction at the bushing/stabilizer bar interface by employing low-friction materials as liners covering the bore of the bushing or by adding lubricants between the bushing and the stabilizer bar. Commonly used materials for bushing liners are polyester or polytetra fluoroethylene while silicone greases have been utilized as lubricants. The primary disadvantage of these designs is that the liner wears or the lubricant dissipates resulting in an unacceptable audible squawk in the vehicle. Also, with these designs, environmental contamination can result in premature wear of the liner or premature dissipation of the lubricant thus leading to the audible squawk.
The designs that allow partial wind-up and then allow slippage of the stabilizer bar with respect to the bushing suffer from the same disadvantages as the designs that allow total rotation in that early wear and/or contamination of the interface between the bar and the bushing can lead to an audible squawk.
The designs that attempt to eliminate all slippage of the bushing have been successful for limited rotation of the stabilizer bar with respect to the bushing, but larger rotation of the stabilizer bar has caused deterioration of the bushing and/or slippage of the bushing. In order to overcome these problems, some prior art designs have incorporated flats on the stabilizer bar or other components which resist rotation of the bushing. While the incorporation of flats has resisted the larger amounts of rotation, the costs and complexities of these designs have limited their applicability.
Still other designs that attempt to eliminate all slippage of the bushing utilize a mechanically bonded bushing assembled over the stabilizer bar and then compress this bushing into an outer sleeve/bracket assembly. While these designs have and continue to meet the needs of the vehicle designers, the bushing which is compressed and assembled into the outer sleeve/bracket assembly can be subject to walk-out of the bushing during vehicle operation.
The continued development of stabilizer bar bushings and attachment systems has been directed toward designs which provide additional durability, eliminate the audible squawking by eliminating the rotation between the stabilizer bar and the bushing but yet still perform the required isolation between the stabilizer bar and the vehicle, and reduce and/or eliminate the bushing walk-out tendency.